Rotary retort furnace



Sept. 2, 1969 A. T. ENK 3,464,683

ROTARY RETORT FURNACE iled Jan. 13, 1967 2 Sheets-Sheet 2 INVENTOR.

3,464,683 ROTARY RETORT FURNACE Albert T. Erik, Toledo, Ohio, assignor to Midland-Ross Corporation, Toledo, Ohio, a corporation of Ohio Filed Jan. 13, 1967, Ser. No. 609,078 Int. Cl. F271) 7/08 US. Cl. 263-34 9 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a rotary retort furnace, and more particularly, to a rotary retort for processing small parts that utilizes direct fired burners without having the work come in contact with flue gases. Use of direct fired burners is accomplished by providing a rotary retort with a seal between the burners and the openings through which the work is discharged. The seal of this invention makes it possible for the retort not only to rotate, but also to move relative to the axis of the furnace without losing contact between the sealing surfaces.

BACKGROUND In the heat treating industry, rotary retort furnaces, such as described in U.S. Patent No. 2,624,561 issued to H. Heyn, have found wide acceptance, particularly for carburizing and hardening of small parts such as wrist pins, bushings, ball and roller bearings, and the like. Because of the large openings provided for discharging work from the retort, it has been necessary to provide the process heat electrically or by indirect fired, radiant tube burners so that a controlled atmosphere can be maintained around the outside of the retort in order that there will be no contamination of the protective atmosphere in the retort during the period in which the work is confined therein. It has been found necessary to limit the peak operating temperature of the heating elements, or radiant tubes, to about 1900 F. in order to avoid frequent maintenance of the equipment. This limitation, in combination with the surface area of the heating elements, determines the maximum processing temperature and the maximum rate at which heat can be transmitted into the furnace to compensate for heat losses and for work requirements. Consequently, many situations arise where the production rate of the equipment is adversely affected by this limitation. Furthermore, the mere addition of more heating surface may not be practical because of space limitations.

To overcome these limitations, as well as realize a substantial savings in equipment costs, it would be advantageous to use a direct fired heating system in place of either electric resistance heating or radiant tube burners. Such a direct fired system, however, normally requires a method for preventing the products of combustion from coming in contact with the work being processed. One such method utilizes a seal around the outer circumference of the retort to prevent the flue gases from entering the retort through the work discharge ports. In such an arrangement, it is also necessary to provide an enclosed chute to protect the parts as they are discharged from the retort.

Prior retorts requiring a protective atmosphere and using direct fired burners have not proven satisfactory for, after prolonged periods of use, especially under conditions of heavy loads and/ or high operating temperatures, the retort will eventually develop a permanent sag. Under such conditions, the designs of the seal around the outer circumference of the retort becomes of utmost importance, as such conditions of misalignment could render the seal useless.

to States Patent 3,454,683 Patented Sept. 2, 1969 It is, therefore, an object of this invention to provide a rotary retort furnace using direct fired burners in which work may be heat treated in a protective atmosphere.

It is another object of this invention to provide a novel seal for use in rotary retort furnaces.

It is still another object of this invention to provide a seal for a retort furnace which will function under conditions of misalignment.

It is a further object of this invention to provide a seal between two members which will remain in contact although one member is at a different temperature than the other.

BRIEF SUMMARY OF THE INVENTION In order to achieve the above objectives and to over come the shortcomings of many prior rotary retort furnaces, this invention provides a rotary retort furnace wherein direct fired burners may be used. The rotatable retort is received by a casting disposed within a refractory housing and the casting and retort are concentric. One end of the retort extends beyond the casting and housing of the furnace and has a pivot point about which the retort may pivot a few degrees. This pivot point also lies upon the axis of the casting within which the retort is disposed. A ball joint seal is provided between the casting and the retort so that the retort may pivot, about its pivotal point, relative to the casting, while the seal between the two is maintained. Intermediate the seal and the pivotal point, the retort has an opening through which work may be discharged. Between the seal and the opposite, or entrance end, of the retort direct fired burners provide heat to the retort. Because of the presence of the seal, flue products do not enter into the retort through the discharge opening. With the ability of the seal to maintain a sealed relationship between the retort and the casting despite pivotal motion of the retort, the retort need not be a perfect right cylinder. That is to say, with the apparatus disclosed herein, the retort may wobble during rotation, as it will normally do after prolonged use, without affecting the effectiveness of the seal.

The features of this invention as described above, as well as other features, will become apparent from the following detailed description and accompanying drawings wherein:

FIG. 1 is a longitudinal view, in section, of a rotary retort furnace incorporating the features of this invention.

FIG. 2 shows an enlarged view, in section, of a portion of the retort and the seal of the furnace in FIG. 1.

DETAILED DESCRIPTION Referring now to the drawing, a rotary retort furnace is shown generally at 10 and has a housing 12, including refractory brick walls 14, that is supported by a plurality of legs 16. The housing 12 has a first opening 20 at the charge end of the furnace and a second opening 18 in the discharge end of the furnace and the refractory walls 14 define a chamber 22. Located within the chamber 22 and received by the second opening 18 is an annular, or bell shaped, casting or shroud 24 having a horizontal axis. The casting is fixedly secured to one end of the housing 12, as by bolts 26, with its axis parallel to the horizontal. The casting has a flange 28 extending about the periphery of its end located within the housing 12.

Disposed within the housing 12 and extending the length thereof is a retort 30 that is received within both openings 18 and 20. The retort 30 and the casting 24 are concentric with the casting circumposing one end of the retort. The retort 30 has a neck portion 32 that extends into the opening 18, and attached to this neck portion is a hub 34 that slightly extends outside of the housing 12. An atmosphere inlet pipe 36 extends through the hub and into the retort 30 to supply a protective gas thereto,

the pipe being secured by a holder 38 that has one end attached to the inside perimeter of the retort. A jacket 40 is attached to the housing 12, and the hub 34 is journaled within the jacket. A flanged bearing member 42 is sealed to the jacket 40 and supports the retort 30 by receiving a shaft 44 that is fixedly secured to and extends beyond the hub 34. The shaft 44 is rotatably received within a channel 46, as well as within the hearing member 42. Disposed between the bearing member 42 and the channel 46 is a sprocket 48 that is fixedly attached to the shaft 44 for rotation thereof. Secured to the outside end of the shaft 44 is a ring 50 that serves as a stop. A roller bearing assembly 52 is provided intermediate the ring 50 and the channel 46 to facilitate rotation of the shaft 44 and ring 50 relative to the channel 46. The channel 46 is disposed upon a track 54 and is free to slide axially thereupon. Secured to the channel 46 is a line 56 that is suspended over a roller 58 and has a weight 60 at the free end thereof. In this way the channel 46 exerts a bias to the right, as seen in the drawing, upon the retort 30 by pushing upon the ring 50 through bearing 52.

At the inlet end of the housing 12, means is provided for feeding work into the retort, which means comprises a chute 62 which enters an opening 64 of the end wall 66 of the retort 30. A sealing member 68 is secured to the chute 62 and engages the end wall 66. A plurality of rollers 70 are provided about the retort at the entrance end so that the retort may be rotated within the housing 12, these rollers being mounted on shafts 72 that are secured within the housing 12.

The retort has a plurality of circumferentially aligned discharge openings 74, in proximity of the second housing opening 18. The casting 24 also has an opening 76 therein and the housing 12 has a well 78 in the refractory brick 14 aligned with the opening in the casting. These latter openings 76 and 78 are intermittently con fluent with each of the retort openings 74 when the retort is rotated about its axis. A sleeve or discharge chute 80 extends from the opening 76 in the casting 24 and through the well 78 of the housing and leads to a receptacle 82 that receives the work. The lower end of sleeve 80 extends into a quenching liquid 84 disposed in the receptacle 82 and forms a seal therewith that prevents access of air into the retort 30.

A seal is provided between the retort 30 and the casting 24, this seal being shown generally at 86. Attached to the flange 28 of the casting 24 by bolts 87 is a sealing member 88 that has an inverted L-shape when viewed in cross section as shown in FIG. 2. The leg of the L of the seal member 88 has a convex surface 90 that faces the opening 20. Secured to the perimeter of the retort 30 is an annular seal member 92 having a concave surface 94 that forms a mating relationship with the surface 90 of the seal member 88.

Disposed within the refractory walls 14 of the housing 12 are a plurality of burners 96 that substantially extend the length of the housing. A flue 98 is located within the top wall of the housing to allow products of combustion from the burners 96 to escape into the atmosphere.

Supported at one end of the housing 12 is a drive line, shown generally at 100, which includes a motor 102 that provides drive through a gear change box 104 and a speed reducer 106 to a sprocket 108. A chain 112 provides a driving connection between the sprocket 108 and the sprocket 48, that is attached to the shaft 44, to rotatably drive the retort 30.

In operation, the retort 30 is rotated by the drive transmitted from the electric motor 102 through the drive line 100 while the casting 24 remains stationary. The retort 30 is heated by the burners 96 which are aligned within the refractory walls 14 and fire into the chamber 22. After the proper temperature is obtained within the retort 30, work is fed through the opening 64 of the retort through the chute 62 and the work may be conveyed through the retort either through gravity (as by tilting the retort 30), its natural angle of repose, or through other means such as helical ribs attached to the inside diameter of the retort. As the retort 30 rotates relative to the casting 24, the surfaces and 94 of the seal members 88 and 92, respectively, slidably abut one another, while maintaining a Sealing relationship. The abutting surface 94 of the seal member 92 about the retort 30 is concave and the abutting surface 90 of the annular member 88 on the casting 24 is convex; therefore, these two members may not only slidably engage one another, but the axis of the retort may vary slightly relative to the axis of the casting 24 without losing contact between he surfaces 90 and 94. It will be observed that the abutting surface 94 is larger than the abutting surface 92 to provide relative movement radially. Referring now to FIG. 2, it is apparent that the seal forms a ball joint type of engagement wherein the retort 30 and the casting 24 may have angular motion relative to one another, as well as sliding motion, without losing the intimate contact between the abutting surfaces 90 and 94 necessary to create a sealing relationship. The mating relationship between the surfaces 90 and 94 are held under compression due to the force imparted upon the retort by the channel 46 and its reaction upon the ring 50. In this particular embodiment the biasing force is to the right as shown in FIG. 2 and is provided by a weight 60 that may be varied, but it is apparent that alternate biasing means may be used to exert a force in either direction as the need may arise, and this biasing means may be in the form of either expansion or compression springs. By thus providing a biasing force upon the retort 30, either pressure may be applied to the surfaces 90 and 94 or a controlled clearance may be maintained therebetween.

The curvalinear surfaces 90 and 94 are disposed upon a radius 110 relative to a point X, indicated by X in FIG. 2. Thus, since the retort 30 and casting 24 are concentric, the retort will pivot about point X without losing the sealing relationship with the casting. In addition, because the retort 30 and casting 24 are concentric, the dimensional changes in each brought about by temperature changes will be proportional to one another, thereby eliminating any misalignment between the two that would tend to aifect the seal 86.

It is readily apparent since the discharge openings 74 of retort 30 cannot communicate with chamber 22 because of the novel arrangement of shroud 24 and seal 86, that products of combustion from burners 96 cannot contact the work within the retort. The products of combustion will tend to escape through the flue 98 although some of the products of combustion could escape past the sealing member 68 about the opening 64 and through opening 20 in the housing 12. The small amount of products of combustion that could escape in this manner will not come in contact with the Work being heated, for this work is fed through the chute 62 directly into the retort 30, and a protective atmosphere is provided in the retort by the inlet pipe 36 which will create a flow of atmosphere opposite to the direction of the path of the work. Thus, products of combustion will be prevented from entering the retort 30 because of the flow of protective atmosphere supplied by the inlet pipe 36.

Although only one embodiment of this invention has been shown and described, it is apparent that changes and modifications can be made therein without departing from the scope of this invention, and it is understood that the preceding descriptions are illustrative only and not for the purpose of rendering this invention limited to'the details illustrated or described except insofar as they are limited by the terms of the following claims.

I claim:

1. A rotary retort furnace for the processing of small parts, the combination comprising: wall means defining a horizontally extending housing having a first opening at one end thereof and a second opening in its bottom wall in proximity of the opposite end, a generally annular member disposed within said housing and secured to the opposite end, said annular member being horizontally spaced relative to said first housing opening and extending over said second housing opening, a generally cylindrical retort received within said annular member and extending therefrom to said first housing opening, and said retort having a first opening in horizontal alignment with said first housing opening and a secOnd opening confluent with said second housing opening, means for rotating said retort about its axis, a ring member secured about the perimeter of said retort intermediate said first and second openings thereof, said annular member having a circular flange about the perimeter thereof that sealingly abuts said ring member to form a seal between said retort and said annular member, said annular member having an opening in the bottom portion thereof, a discharge tube extending from said retort through said annular member opening and said second housing opening, and means for heating said retort disposed Within said housing.

2. A rotary retort furnace for the processing of small parts, the combination comprising: a housing having first and second openings, said openings being horizontally annular casting secured within said housing and having a portion received by said first opening, a generally cylindrical retort disposed within said housing and extending from said first opening to said second opening, said retort being disposed within said casting and having a portion extending outside said housing through said first opening, bearing means supporting said outside portion of said retort, means for feeding work into said retort through said second opening, means for rotating said retort about its axis, said retort having a ring member secured about its perimeter, said casting having a circular flange attached to its perimeter that abuts said ring member to form a seal between said retort and said casting, means connected to said retort for controlling the sealing pressure between said ring member and said circular flange, said retort having a work discharge opening intermediate said seal and said first housing opening, a discharge tube extending from said retort through said casting and said housing whereby said discharge tube i periodically confluent with said discharge openings when said retort is rotated, burner means longitudinally disposed within said housing operative to heat said retort, and flue means provided to said housing.

3. A rotary retort furnace for the processing of small parts, the combination comprising: wall means defining a housing having first and second openings spaced relative to one another, an annular, bell-shaped casting secured within said housing with its neck portion disposed within said first opening, a generally cylindrical retort disposed within said housing and extending from said first opening to said second opening, said retort having a necked down portion at one end thereof that is disposed within said neck of said casting, a pipe received within said retort through said necked down portion, means for supplying gas to said pipe, a ring member attached about the perimeter of said retort, said ring member having a mating surface circumposing said retort, said casting having a circular flange disposed about the large end thereof, said circular flange having a mating surface in sealing engagement with said ring mating surface, means connected to said retort for controlling the sealing pressure between said mating surfaces, one of said mating surfaces radially engaging only a portion of other said mating surface, means for rotating said retort relative to said casting, mean for heating said retort, means for discharging work from said retort intermediate said mating surfaces and said first opening, whereby said first and second mating surfaces form a seal as said retort rotates and said one of said mating surfaces is operative to move radially relative to a point on the axis of said retort and still maintain a sealing relationship with the other of said mating surfaces.

4. The furnace of claim 3 wherein said heating means comprises a plurality of direct fired burners disposed within said housing and said housing has a flue therein for disposing of products of combustion.

5. The furnace of claim 4 wherein one of said mating surfaces is concave and the other is convex.

6. The furnace of claim 5 wherein said ring mating surface is concave and said flange mating surface is convex.

7. A rotary retort furnace for the processing of small parts, the combination comprising: wall means defining a housing having first and second openings horizontally spaced relative to one another, a generally cylindrical retort disposed within said housing and extending from said first opening to said second opening and having a discharge opening within its perimeter in proximity of said first housing opening, a chute confluent with said discharge opening and extending from the bottom of said retort through said wall means, a shroud member sealingly attached to said housing and disposed about said retort member, a ring member circumposing and sealingly attached to said retort, said ring member having a mating surface facing said shroud, a circular flange sealingly attached to said shroud member, circumposing said retort and having a mating surface in engagement with said ring mating surface to form a seal between said retort member and said shroud member, one of said mating surface radially engaging only a portion of said other mating surface, direct fired burners disposed within said Wall means, means for rotating said retort about its axis.

8. The furnace of claim 7 wherein said ring mating surface is concave and said flange mating surface is convex.

9. A rotary retort furnace, comprising in combina tion: wall means forming a generally longitudinally extending housing having first and second end walls; Wall means forming a generally cylindrical retort disposed within said housing having a first end adjacent said first end wall and a second end adjacent said second end wall, said retort having a discharge opening in said retort wall means adjacent its second end; a ring member attached to the outer periphery of said retort between said dis charge opening and said first retort end, said ring member having a mating surface thereon; a shroud member concentrically circumposing the second end of the retort, one end of said shroud member being sealingly attached to said housing and the other end having sealing means comprising a mating surface adapted to co-act with the mating surface of said ring; means for urging the mating surface of said ring into contact with the mating surface of said sealing means; a discharging chute extending through said housing, sealingly attached to said shroud and confluently aligned with the diametrical plane of said retort containing said discharge opening; means for feeding work to be treated to the first end of said retort; and means for rotatably driving said retort, whereby the work to be treated which is fed into the inlet end of said retort passes longitudinally through said retort and passes out of said discharge opening and into said discharge chute.

References Cited UNITED STATES PATENTS 2,207,987 7/1940 Kent et al. 26334 2,413,933 1/1947 Van Doorninck 263 -34 2,624,561 1/1953 Heyn 26334 2,659,588 11/1953 Blanchard 26332 2,856,173 10/1958 Enk et al. 26334 X 2,898,099 8/ 1959 Coriolis 263--34 3,386,719 6/1968 Martin 26334 EDWARD G. FAVORS, Primary Examiner UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,464,683 September 2, 1969 Albert T. Enk

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 15, "over" should read over- Column 4, line 14, "he" should read the Column 5, line 24, after "horizontally" insert spaced relative to one another, a generally line 44, "openings" should read opening line 62, "large" should read larger Signed and sealed this 28th day of April 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, :11.

Commissioner of Patents Edward M. F lctcher, Ir.

Attesting Officer 

